Looks intel only, but they don't provide the source on the vmac site. It'd take quite a lot of work to adapt to black hardware, you'd want a lot of optimisations to use 680x0 native calls not emulated. Something like ShapeShifter from the AmigaOS world would be much more effective on NeXT black hardware. At one point, Amigas with 68060 accelerators running ShapeShifter were the fastest Macs around, beating even Quadras. So ShapeShifter ported to NextStep would be a nice solution.